“The crop coming these days is discolored, which makes it unfit for extraction. No processor is willing to purchase the same from us,” said Ashwani Kumar of Aggarwal Traders, one of the leading purchasers of mustard seed in the area.

He said extensive damage to the crop in the main growing areas had not only impacted arrivals but has delayed extraction and crushing of oilseed.

“By this time, mills should have managed to procure almost half of their annual mustard need, but not even 10 per cent has been purchased,” another trader said.

According to agriculture ministry’s own estimate, mustard seed crop in around 2.6 million hectares of land has been damaged in the recent bout of unseasonal rain and hailstorm that hit 13 states in the first fortnight of March.

In 2014-15, the crop has been planted in 6.6 million hectares, which translates into damage of almost 40 per cent area (see chart).

In Rajasthan, the country’s biggest producer of mustard seed, the crop in 1.5 million hectares has been flattened.

Mustard is usually sown thrice during the season, between October and the middle of December. Officials said almost all the late sown crop had been damaged.

“Those farmers who had planted their crop around November have seen the maximum damage,” said Rajesh Keshri, spokesman of Puri Oil Mills, a leading mustard oil manufacturer of North India.

He said preliminary estimates show this year’s crop could be at least 5-10 per cent less than the estimate. The central government, in its second advance estimate, had pegged 2014-15 mustard seed production at 7.36 million tonnes (mt), around 0.51 mt less than last year.

A damage of 5-10 per cent to the current estimate could further lower this output to 6.6-7mt. Mustard is one of the premier oilseeds grown in India, having the highest oil content. A significant decline in output could push up annual edible oil imports, already expected to be at a record high in 2015-16.

India received 49.2 millimetres (1.9 inches) of rain between March 1 and 15, almost three times the average, data from the India Meteorological Department showed. The rains not only damaged crops but claimed around 10 lives. The Centre has declared the unseasonal rains and hailstorm a national calamity.